The object of the present invention is a particle resistant to storage, especially a particulate carrier for carrier-bound reactions, detection and/or isolation processes, a process for the production of this particle resistant to storage, and uses of the particle according to the invention.
Particulate carriers consisting of a solid core and a polymer are known as such and have already been used for many purposes. In particular, such particles have been used for immunoassay markers to bond a solid core by means of polymers, e.g., biopolymers, to an affinity component. As particulate material especially sols of metal particles, e.g., magnetic iron particles of colored gold particles, nonmetallic particles, e.g., selenium, coal dust, SiO2 or ceramic particles, corpuscles or even latex particles of another polymer with different (bonding) properties have been used.
Thus, U.S. Pat. No. 4,230,685 describes an improvement of the bonding of specific binders to magnetic particles, whereby a particle is coated with an acrylate polymer or a polysaccharide, whereby protein A is bonded to this coating by glutaraldehyde.
U.S. Pat. No. 4,452,773 describes the production of magnetic iron-dextran microparticles. These particles have a size of from 100-700 xc3x85, in particular 300-400 xc3x85. A large number of the particles are colloidal and ferromagnetic with a dextran shell. The obtained particles are functionalized by periodate oxidation.
EP-B-452,342 concerns super-paramagnetic particles coated with polysaccharides having colloidal size. The particles can be bonded to additional groups. By sorting out the particle mixture into size subtractions having uniform magnetizations there are obtained compositions having homogeneous properties with regard to the retardance thereof within a magnetic field. The possibility to separate with respect to size is mentioned. Preferred are coatings from polysaccharides or proteins. Polysaccharides are functionalized by periodate oxidation. In addition, functionalization with bromocyanogen is possible. The bonding of the protein shell to particular molecules can be effected by side chain amino groups or sulfhydryl groups.
DE-A-40 37 724 relates to devices for immunoassays in which a direct or indirect markers are used. Direct markers are preferred as they do not require additional steps to visualize test results. Examples for direct markers are metal sols, dye sols, latex particles, color indicators, colorants located in liposomes, and nonmetal sols such as a carbon sol. Another aspect of DE-A-40 37 724 relates to an immunochemically active marker. Then, a coal dust particle is bonded adsorptively to a ligand or a ligand conjugate. The sensitivity of the test for, e.g., human choriongonadotropine hCG is denoted as 25 mIU/ml (IU=international unit).
EP-A-0,410,893 describes a process for the determination and recognition of an antibody within biological fluids directed against a specific antigen. The listed insoluble carrier particles comprise cells, gelatin particles, microcapsules, organic polymers, inorganic fine particles, or colloidal particles of metal or metal compounds being finely dispersed with bovine serum albumin or cholesterol.
Also EP-A-0,032,270 describes a quantitative and/or qualitative determination of an immunologic component using one or several marked compounds being obtained by a direct or indirect coupling of such component(s) to particles from an aqueous dispersion of a hydrophobic dye or pigment or polymeric cores being coated with such dyes or pigments.
EP-0,321,008 relates to a process for the determination of one or several components of a reaction between a specifically bonding protein and the corresponding bondable substance within a sample, the mutual activity of such components and of at least one marked component being obtained by coupling or adsorbing sol particles of the marking directly or indirectly to the component. Preferred sol particles are phosphorus, carbon and/or silicon. Agglutination and aggregation can be prevented by covering the particles with macromolecules containing polar groups such as proteins, poly(ethylene glycol), polymeric carbohydrates, poly(vinyl alcohols), and similar ones. Suitable protective proteins are antigens, antibodies, and anti-antibodies. Immunochemically inert materials such as, e.g., albumin, poly(ethylene glycol), or other polar macromolecules may be used as well. The test sensitivity, e.g., with respect to rabbit immunoglobulin G, is specified as 1.5 ng absolute.
EP-0,298,368 concerns a process for carrying out a diagnostic immunoassay by using colloidal iron metal containing particles having a conjugate attached to them being capable of recognizing specifically the analyte to be determined. The test sensitivity for hCG is in the mIU/ml range.
EP-A-0,280,560 discloses Streptococcus A antigen antibodies being bonded covalently to core/shell polymer particles, the shell being formed from poly(mp-chloromethylstyrene) and the core from poly(styrene-co-2-acetoacetoxidethyl methylacrylate), containing Oil Red EGN within the core to obtain a agglutination reagent.
U.S. Pat. No. 4,452,886 describes the polymerization of lysine with glutaraldehyde and Congo red to colored particles. The test sensitivity for hCG is in the 1000 IU/ml range.
W. P. Collins describes in his book xe2x80x9cAlternative Immunoassaysxe2x80x9d, John Wiley and Sons, Chichester, N.Y., etc., in the chapter xe2x80x9cDisperse Dye Immunoassay (DIA)xe2x80x9d on page 48-49 the advantages of particle markers and points out the significance of the essential parameters such as particle size, distribution and form, solubility in organic solvents, colloid stability, and bonding capacity, e.g., for antibodies. The test sensitivities mentioned by him are in the mIU/ml range. The conjugates are stable for at least 15 months if they are stored in the lyophilizated state at xe2x88x9220xc2x0 C. or 4xc2x0 C.; aqueous conjugates should be consumed within 6 days after preparation.
JP-A-0686771 relates to encapsulated toners and the production thereof.
The inert cores described in the art have been suffering from obvious drawbacks. In case the cores are polymerized therein, the desired core property is impaired too much. In case the polymer is adsorbed on the core with a subsequent covalent or other bonding of the affinity component, the bonding of the core in most cases is too weak, so that the stability is not ensured at longer term. In addition, by employing the methods according to the art only the bonding of one or a small amount of reactive and affinity components is achieved.
The object of the invention consists of providing stable particles with characteristic usable properties, especially marking properties, allowing, if necessary, also numerous reactive components at the same time to be stably bonded thereon. Stability should in particular also comprise a storage at longer terms.
The present invention provides a particle resistant to storage, especially a particulate carrier according to the features of claim 1. Dependent claims 2-18 relate to preferred embodiments of the according to the invention particle. Claim 19 together with the appropriate dependent claims 20 and 22 relate to a process for the production of the particle according to the invention resistant to storage. Claims 23-31 relate to uses of the particle according to the invention.
The particle according to the invention resistant to storage is especially destined for carrier-bound reactions, detection and/or isolation processes. It consists of at least a first and a second component, the particle being suitable to be provided with a reactive component, especially a specific reactive component. The second component consists of a crosslinkable polymer and forms more or less a shell enveloping and/or enclosing the first component as the core at least partially.
The first component has at least one ascertainable property. On the second component there may be arranged reactive components. The particle resistant to storage is characterized by its manufacturing process and available by reacting the first component with the crosslinkable polymer, thereafter reacting the formed product with a crosslinking agent such that the first component is arranged within the second component resistant to storage.
Preferably, the reaction conditions are adjusted such that the first component is enveloped and/or enclosed by the second component in a reticular manner.
The second component forming the carrier according to the invention is preferably a polymer having active or activatable functional groups being able to react in one respect with the crosslinking agent or else with the reactive components or with both of them. The polymer forming the second component of the carrier according to the invention can also be produced from several crosslinkable polymers and/or crosslinkable monomers. Then, the polymer can be produced from proteins and/or polyamides with functional groups. In principle, also other polymers such as biopolymers or rather monomers are possible as far as crosslinking is achievable. Preferably, the second component is crosslinkable with at least bifunctional compounds.
Preferably polymers are used which stabilize the aqueous suspension of component 1 adsorptively, that is, especially polar polymers.
The reactive components arranged at the second component of the particle according to the invention are especially molecules or molecular groups possessing affine properties towards other substances. These include especially enzymes and substances interacting with enzymes. Then, on the one hand the substrate or on the other hand the enzyme can be arranged at or on the second component as the reactive component. Antibody/antigen, biotin/streptavidin behave likewise. Streptavidin or biotin in form of a specific reactional component bonded stably to the dye possesses the advantage the dye is universally usable as a co-reactant for biotinylated components or those coupled with streptavidin. These can on their part possess entirely different functions, e.g., act again specifically against another component or as a catalyst. In addition, nucleic acids of RNA or DNA types are usable within the meaning of the carrier according to the invention. The nucleic acids are able to hybridize with the corresponding complementary or partially complementary strands depending on the stringency of the reaction conditions and to form stable complexes. Consequently it is possible to identify specific nucleic acid strands within a sample to be investigated and to process further on the basis thereof. In addition, combinations of the reactive components can be arranged at or on the second component. Then, in accordance with the invention one obtains carriers which are applicable for different problems.
By selecting the crosslinking agent and the concentration thereof and adjusting specific processing conditions, the crosslinking reaction can be controlled such that the second component envelops the first component more or less in a molecular net, the meshes thereof possessing a narrow mesh size distribution.
At the same time, by means of the processing conditions of crosslinking there can be adjusted the number of free binding sites at the surface of the particle which remain free due to the binding of the at least bifunctional crosslinking agent with only one function to the surface for an additional binding, especially of reactive components. The created number of binding sites can be used completely or partially with a defined portion after a partial saturation.
In particular, by means of the processing conditions the thickness of the shell can be adjusted, whereby the homogeneity thereof subsequently still can be increased by a fractionation. A multi-step covering process can still improve the inclusion of the first component.
The first component of the particle in accordance with the invention do possess at least one ascertainable property component 2 and/or the reactive components bonded thereon do not possess with regard to the quality thereof, such as absorptivity or emissivity of electromagnetic waves, mass, magnetism, dielectricity, radioactivity, size and/or density.
As ascertainable properties the core as the first component of the carrier according to the invention can possess there are understood also a pharmacological-biological effect as well as a catalytical effect or combinations of these. So, for example the absorptivity or emissivity of electromagnetic waves can be produced by respective chromophores or fluorophores. The properties mass, size, and density are interconnected physically and can be adjusted accordingly by, e.g., particles with a higher specific density. The property of size can be used advantageously for agglomeration and the property of mass for gravimetry. Agglomeration is advantageous for the specific precipitation of components in solutions or microemulsions. The first component can be provided with the property of radioactivity by radioactive marked structures. Similarly the other specified properties can be connected with the first component. The first component can as well be a capsule containing liquids or particles which cannot be enclosed sufficiently (for example particles being extremely small or instable in solution).
In an advantageous design of the carrier according to the invention the carrier is such that the first and second components are connected separably with each other. The connection between first and second components is effected by enclosing the first component within the second one. Basically, it is possible to expose the first component by removing, if necessary, the second component to facilitate a detection of the properties connected with the core by measurement techniques. Removing the second component can be performed, e.g., in case of proteins by appropriate proteolytic enzymes. These degrade the shell such that the core remains. The latter can further be treated in accordance with its property to be measured. In addition, it is possible to dissolve the core from the connection of first/second component by treating it with a medium wherein the core dissolves preferably, so that in the end an xe2x80x9cemptyxe2x80x9d shell remains, or to dissolve the complete particle by means of a total solvent. So, e.g., if a dye soluble in ethanol is enclosed by the second component, it is possible to treat with the solvent and to measure the obtained ethanolic solution spectroscopically. If the conditions are standardized and, if necessary, calibrated, a corresponding discoloration can be used as a quantity for quantitative determinations.
In addition to the individual particulate carriers resistant to storage the embodiments thereof also possess a great significance in performing methods of application. Then, the particulate carriers resistant to storage present themselves in majority in form of populations. For the application of the particles according to the invention the carriers are preferred to be present in populations being distinguished by a narrow size distribution of the individual carrier particles according to the invention.
It is especially preferred that the population possesses carrier particles having as well a narrow range of the shell size distribution as a narrow range of the core size distribution and consequently a narrow range of the shell/core size distribution. Also for other properties there is desired a homogenous distribution, e.g., of the color intensity or the magnetizability, for the core, especially for the entire particle.
In the practical use of the particle according to the invention as a carrier it is advantageous to arrange a high concentration of reactive components at or on the second component. Because of this there can be achieved relatively high bonding constants to corresponding complementary structures in immunoassays, although the individual reactive component and its corresponding complementary structure possibly possess only an average bonding constant. However, due to the multiplicity of binding sites the effectiveness of bonding (avidity) is increased.
A process for the production of the carrier according to the invention comprises the steps of reacting the first component with a crosslinkable polymer at least one time. Then, the polymer can be adsorbed physically at the surface of the first component. The crosslinkable polymer will then, subsequently to further processing steps, form the second component. This is effected by a treatment with crosslinking agent. As crosslinking agents there are possible especially bifunctional molecules such as glutardialdehyde, dicarboxylic acids, acrylates, methacrylates. Then, the crosslinking agents having olefinic groups are activatable by, e.g., photo reactions or other free-radical chain reactions. The functional molecules can crosslink the polymers in particular via condensation or addition reactions.
Optionally, the first component before the treatment and/or the intermediate product together with the second component and/or the particle can be subjected to a separation by size and/or by another property to achieve a distribution of size and/or of another property as homogenous as possible. It is preferred to perform the treatment of the first component with polymers two to three times, and it is especially preferred to perform a separation by sizes.
The process is particularly advantageous as it is possible to homogenize the first component and to adjust the concentration thereof within the suspension initially, irrespective of a reaction. Depending on the first component used there can be employed standard processes for the homogenization and stabilization of the suspension. Preferably the second component is used to stabilize the suspension if it is a polar compound with a sufficiently good adsorption at the first component. The ratio of the concentrations of the first and the second components is selected such that a suitable thickness of the shell is achieved by adsorption. In the multistep process the thickness of the shell is selected preferably thin. Other parameters such as time and temperature can be used as well to influence the adsorption. Thereafter, the intermediate product can be re-homogenized. To achieve a good crosslinking of the shell, especially within the inner area near by the first component, the crosslinking component is added in an excess of several orders of magnitude. In addition, the effect of the crosslinking component can be influenced by other parameters, in particular the contact time as well as the number of formed reactive groups on the surface due to single-side bonded crosslinking molecules which number can be reduced by partial blocking subsequently.
The carriers according to the invention are preferably used in assay techniques such as immunoassay, solid-phase assays and/or chromatographic assays. In addition, they can be used as vehicle for the affinity transport of effective substances if for example pharmacologically active substances as the first component are enclosed by the second component. As affinity transport there is to be understood, e.g., transports of pharmacologically active substances by means of antibodies being located at the second component and bonding specifically to a particular target structure.
Particles with a radioactive core can be used advantageously, too, as they act or are concentrated due to the affinity transport above all at the location of application, and therefore lower overall radioactivity doses can be used, whereby a systemic strain can be kept within narrow limits.
The use of the particulate carriers resistant to storage according to the invention as a catalyst for chemical reactions is advantageous as well. Accordingly, for a rapid intermixture of the carrier-bound catalyst (biocatalyst) with the reaction mixture there can be used a magnetic core, the weight of which subsequently provides a rapid separation.